Prophylactic Hydration for Contrast-induced Nephropathy

Contrast-induced nephropathy refers to the decline in renal function that can occur as an adverse reaction to the intravascular administration of iodinated contrast media.

High-risk patients who did not receive guidelines-recommended prophylactic hydration prior to procedures requiring iodinated contrast media had the same rate of contrast-induced nephropathy (CIN) as patients who received usual care, according to results from the phase 3 AMACING trial published in TheLancet.1

CIN refers to the decline in renal function that can occur as an adverse reaction to the intravascular administration of iodinated contrast media. Various international guidelines state that in order to prevent CIN, patients at high risk should receive intravascular volume expansion with isotonic saline prior to contrast media administration, a recommendation that the AMACING (ClinicalTrials.gov Identifier: NCT02106234) investigators say is based on expert opinion, not clinical trials.

Patients were defined as high-risk on the basis of criteria described in The Netherlands and European guidelines. Patients with an estimated glomerular filtration rate (eGFR) lower than 30 mL/min/1.73 m2, a history of dialysis, or no referral for intravenous hydration were not eligible for the study.

Results showed that 8 out of 307 patients (2.6%) who received no prophylactic hydration and 8 of 296 patients (2.7%) who did receive prophylactic hydration developed CIN, an absolute difference of −0.10% (one-sided 95% CI −2.25 to 2.06; one-tailed P =.4710). Mean total costs were €1455 for the hydration patients and €792 for non-hydration patients (mean difference H– minus H+: −€663, 95% CI –€1234 to −€191).

In an accompanying editorial, Peter A. McCullough, MD, and colleagues criticized the study’s methodology.2 “The method of computation of the non-inferiority margin and the revision of this statistical approach was unconventional and in the end had the assumptions that the contrast-induced acute kidney injury rate in the normal saline group would be 2.4% and the rate in the no saline prophylaxis group could be as high as 4.5% with relative risk or hazard ratio of less than 1.88 to meet non-inferiority. The upper bound of the 95% confidence limit for this construction is about 4.50, which exceeds all conventions for non-inferiority trials,” they wrote.

Dr McCullough and colleagues also expressed the opinion that the field is not ready for non-inferiority trials due to the absence of a proven standard for prophylactic hydration that can be applied in control groups. However, Ms Nijssen stated in an interview with Rheumatology Advisor that a non-inferiority design was the only appropriate choice for evaluating the cost-effectiveness of prophylaxis.

“The efficacy of prophylaxis had not been shown, and it was not known what CIN incidence would be in patients not receiving any prophylaxis. We assumed that the prophylaxis might be better in reducing CIN than not giving any prophylaxis but that the costs and patient burden imposed would also be much greater, as well as the risk of complications due to prophylaxis,” she commented.

Ms Nissen added: “Because in most cases CIN is a transient rise in serum creatinine — a biochemical event which resolves by itself within a few weeks and which only rarely leads to lasting clinically relevant effects — we determined that a non-inferiority margin of 2.1% would be acceptable. That is, we determined that not giving prophylaxis would be non-inferior to prophylaxis in that it saves costs and reduces burdens on patients, as long as the difference in CIN between the 2 groups was not greater than 2.1%.”

Summary and Clinical Applicability

Ms Nijessen told Rheumatology Advisor thatphysicians could consider not giving prophylactic hydration to the population described in the study, assuming optimal contrast administration. “It must be noted that clinical practice should not be changed based on a single study,” she stated.

“However, in this case one could ask whether the guidelines should have introduced this prophylactic hydration as standard care, since its efficacy had not been shown. Also, we found complications of the prophylactic hydration occurring in 5.5% of patients, which poses concerns regarding the ethics of using prophylaxis. Lastly, there are several studies in recent years that generate some doubt as to cause and consequences of CIN.”

Study Limitations

The study took place at a single center

The sample size was smaller than planned

The design of the study was open-label by necessity

Post-contrast serum creatinine measurements were not available in all patients